Who's taking care of who? Vera plays Jenga with Alyce, 15, at the Hackney Young Carers Project. Photograph: Teri Pengilley for the Guardian

Approximately 9% of men and 12% of women in England and Wales do it, but it's easy for their work to become invisible to policymakers and statisticians: unpaid care.

A new release from the ONS on Thursday has sought to take a closer look at this work, its growth and most of all, the impact on those who provide it.

The report finds young carers face a disproportionate impact on their health. Before taking a look at some of the other trends, it's important to be clear on what the ONS means when it talks about unpaid care:

A person is a provider of unpaid care if they look after or give help or support to family members, friends, neighbours or others because of long-term physical or mental ill health or disability, or problems related to old age. This does not include any activities as part of paid employment.

No distinction is made about whether any care that a person provides is within their own household or outside of the household, so no explicit link can be made about whether the care provided is for a person within the household who has poor general health, or a long-term health problem, or disability.

Age

Those aged 50-64 shouldered the greatest part of the responsibility for unpaid care in England and Wales, and there are more women than men in this category. The report suggests a number of reasons for this - women in their 50s are more likely to leave the labour market to provide care, they retire earlier and the peak in this age group might be because those aged over 65 need care themselves.

Young carers, those aged under 24, make up around 5% of all unpaid carers (around 289,000 people) but - as the following sections consider - may struggle more than other age groups with the responsibility of providing care for free.

Health

Because this data was part of the 2011 census, it's been possible to compare how the health of unpaid carers compares to that of the general population. When asked to rate their health by choosing one of five categories ('very good', 'good', 'fair', 'bad' and 'very bad'), those providing unpaid care were more likely to reply 'not good' than those not providing care. The trend of lower reported health were true across regions, ages and genders.

The difference between those providing 50+ hours per week of unpaid care and those providing none at all (shown below using the black line) was most pronounced for under 24 years of age. Whether male or female, the youngest unpaid carers are almost five times more likely to state they're not in good health than their counterparts who don't provide this service.

Economic position

Though unpaid care is more common among part-time workers, it may come as a surprise just how small the difference is between economically active and the economically inactive. For example, 2.2% of economically inactive women provide 20 to 49 hours unpaid care - for economically active women, that figure only falls to 1.6%.

Unsurprisingly, this correlated with the other factors described here. So the more unpaid care you provide, the more likely you are to state your general health is 'not good' - and nowhere is this trend more noticeable than for those who state their economic position is that of 'student' (many of whom are also likely to be those aged 0-24).

The data also shows that the gender gap is less pronounced for the economically inactive - but as the next section shows, that trend is not noticeable across the board.

Gender gap

Across all regions in England and Wales, women were more likely than men to be the providers of unpaid care. This inequality (see the chart below) has had particularly disadvantaged women wanting to take up work opportunities or remain in employment according to the ONS report.

The gap between men and women narrows slightly in retirement. Surprisingly however, a greater proportion of men than women state that they are 'looking after the home or family', especially when providing more than 50 hours of care a week.

You can watch the video which the ONS released with the data here (warning: it is particularly dry).

This is the last of three posts on today's 2011 Census data release. Our analyses of the latest figures on the UK's foreign-born population and religion can also be found on the Datablog site.